Microstructure and coercivity mechanism of highly textured Nd-Fe-B films

The coercivity mechanism of highly textured highly coercive Nd-Fe-B films has been investigated in relation to their microstructures. With increasing deposition temperature, the microstructure of the films changes from a rounded to rectangular grain shape with no significant change in the grain size. At the same time, the degree of c-axis orientation improves. Scanning electron microscopy reveals a low wetting capability of Nd and Nd₂Fe₁₄B on the Ta buffer layer, which could explain the large roughness of the films. A coercivity analysis has been performed to correlate the microstructural features with the magnetic behavior. From this analysis, it can be concluded that the improved texture at higher temperatures leads to an overall improvement of the coercivity, although the sharp edges of the resulting rectangular grains reduce this effect.